Hydroisomerization of n-hexane over gallium-promoted sulfated zirconia

Abstract

Gallium-promoted sulfated zirconia (GSZ) catalysts were prepared by impregnation of zirconium hydroxide with aqueous Ga 2(SO 4) 2 followed by calcination. Isomerization of n-hexane was studied over GSZ at 150 °C, 2.0 MP, WHSV 2 and H 2/hexane (molar) ratio of 5. In comparison to sulfated zirconia (SZ), the conversion of n-hexane over Gallium-promoted sulfated zirconia (GSZ) was greatly improved and it remained stable at 85%. In particular, almost all the products were isomers of hexane and the selectivity of 2,2-DMB reached 20%. The results of characterization indicated that the addition of gallium onto SZ catalyst showed little difference in acid strength between SZ and GSZ catalysts while the redox properties of the SZ catalyst changed with addition of gallium. The transformation of SZ crystalline from metastable tetragonal phase, the more active phase, to monoclinic phase was retarded with the addition of gallium. Furthermore, the simultaneous promotion of Pt and Ga brings the production distribution very close to the equilibrium one.